The invention relates to an electromotively adjustable, focusing drive for a microscope. The microscope may be finely or coaxially adjusted by a manual control.
One prior art device having conventional fine-setting knobs is disclosed in German Offenlegungsschrift No. 3,410,201. These manually operated knobs, located on the microscope, are mechanically connected by means of a shaft to the object stage adjustment mechanism. A motor coupled to the shaft via a magnetically shiftable clutch and gearing means effects a moving object stage coarse adjustment. The disadvantages of this system, however, are the large number of components that must be mechanically moved and the associated high manufacturing costs.
An electromotive drive for the focusing of a microscope objective is disclosed in German Offenlegungsschrift No. 2,262,614. For both the coarse and fine drives, an electric motor, in each case, is connected via a gearing means to the object stage, which is displaceable in the z direction. On the microscope foot, two rotary switch knobs are arranged, these being rigidly interconnected via a shifter rod. By turning the switch knobs to certain positions, electric contacts operate, which, in turn, close the circuit to operate either the fine setting motor or the coarse setting motor.
Apart from the considerable mechanical elements required, operating one of the switch knobs has the effect of triggering only one signal, either for the coarse drive or the fine drive. It is not possible, however, to perform a sensitive focus setting by a corresponding, rotary movement of the switch knob.
A device for the manual operation of an electromotively adjustable focusing drive is known from German Utility Model No. 8,606,168. In this publication, a control desk separate from the microscope is disclosed, in which case a handwheel for the manual fine adjustment of the focusing drive is connected to a digitally operating encoder. By operation of the handwheel, digital pulse sequences are generated via the encoder and fed to a downstream control circuit. The latter then controls the motively adjustable focusing drive. Apart from the considerable circuitry needed, a further disadvantage is that no combined coarse-fine adjustment, by means of a single manually adjustable control element, is possible.